Learn To Gauge?

At the receiving end of some advice earlier today (which is not surprising given the bumpy road on which my life is traveling), I was told that I should "learn to gauge". Some background for the clueless reader - the talk was about people. Interesting thing this, I thought. How should I learn to gauge things about people? Well maybe, by generalizing - if I can figure out what people do or how they think in certain situations then maybe I can gauge whatever it is that I am supposed to gauge. But then this same kind hearted soul pointed out a major flaw in the above hypothesis - "people are different and they may not always think and react in the same way".
Well, this got me confused... Isn't there something known as rationality and logical thinking? Yet there are people who don't think and act in the same way (as I was told) and hence concluded that they don't necessarily act and react logically. I know that all humans aren't machines (heck even machines don't always act in the same logical way), so I would think it safe to accept a small margin of variance in terms of logical behavior but not enough to proclaim that no rule can be made of it (calling the variances - exceptions). Another useless hint for the still clueless reader - A 'specific subset' of all people was the target group being spoken about.
So, here I am, still left with the fundamental question of "How to gauge"? Well, people of the world (or the subset under consideration here), hear, think and understand:

"Life will be made much easier if what you want the other person to know is communicated explicitly. Speech, written words, instant messengers, SMSes, emails etc are the various means at your disposal to achieve this objective. Use them. Telepathy is NOT a reliable medium yet. Please do not expect others 'to gauge' or worse still, to 'somehow know' what you want them to.
For those of you don't agree, since I still have to share this planet with you, I am trying to learn 'to gauge'... Any help in this regard would be highly appreciated!"